How to compare the environmental impact of products with a life cycle assessment, why recycling and reuse help, and new ways of getting copper from poor ores.
Objectives
Describe the stages of a life cycle assessment and say why it is not a purely objective process.
Interpret and compare life cycle assessments for products such as shopping bags.
Evaluate ways of reducing the use of limited resources, including reuse and recycling of metals and glass.
Evaluate phytomining and bioleaching as alternatives to traditional mining.
Life cycle assessments, recycling and getting metals sustainably explained
Start here
Every product we use has to be made from something, shipped somewhere, used and then thrown away or recycled. Each stage uses resources and affects the environment.
This matters because many raw materials are limited and mining, quarrying and rubbish all damage the environment. A life cycle assessment helps people compare products fairly.
By the end you will be able to describe the stages of a life cycle assessment, interpret LCA data, and evaluate recycling and other ways of saving resources.
Reduce, reuse, recycle
Metals, glass, building materials, clay ceramics and most plastics are made from limited raw materials. Much of the energy used to make them also comes from limited resources such as coal, oil and gas. Quarrying and mining cause environmental damage.
We can reduce the use of limited resources by using less, reusing and recycling. Some things can be reused. A glass bottle can be washed and filled again. Others cannot be reused and are recycled into a different product. Glass can be crushed and melted to make new glass products. Metals can be melted and recast, or reformed into different products.
The amount of sorting needed depends on the material and on the properties the new product needs. For example, some scrap steel can be added to iron from the blast furnace. This reduces the amount of iron that has to be extracted from iron ore.
Why recycling metals matters
Recycling metals saves ore, so the supply lasts longer. It usually saves energy as well, because melting scrap needs less energy than extracting a metal from its ore. It reduces the amount of rubbish sent to landfill. It also cuts the damage from mining and the pollution from extraction.
There are costs too. Scrap has to be collected, transported and sorted, and these jobs need energy and money. Mixed metals may need separating before they can be reused.
When you evaluate, give an advantage, a disadvantage and a judgement. For example, recycling aluminium saves a lot of energy and money, so it is usually worth doing even when the costs of collecting and sorting are included.
Life cycle assessment
A life cycle assessment (LCA) is a way of comparing the environmental impact of a product at each stage of its life. The four stages are: extracting and processing raw materials; manufacturing and packaging; use and operation during its lifetime; and disposal at the end of its useful life. Transport and distribution at each stage are included.
The use of water, resources and energy, and the amount of waste produced, can be measured fairly easily. It is harder to put a number on the effect of a pollutant. This needs value judgements, so an LCA is not a completely objective process.
A selective or shortened LCA can be misused. A company may leave out the stages that make its product look bad and use the result in advertising. A careful LCA compares the whole life of the products.
A flow of four life cycle stages: extracting and processing raw materials, manufacturing and packaging, use and operation, and disposal at the end of its useful life. Transport and distribution are counted at each stage.
Comparing shopping bags
A typical LCA question compares a plastic bag with a paper bag. The table shows made-up figures for practice, for one bag of each type. Use the numbers to compare each stage.
The plastic bag uses less energy and less water to make, and less raw material, but it stays in the environment for a long time if it is thrown away. The paper bag needs more energy, water and trees to make, but it rots away. How the bag is used matters. A bag reused many times has a smaller impact for each use.
To compare fairly, divide the impact by the number of uses. A paper bag with an impact of 1.5 units that is used 3 times has 0.5 units per use.
Interpreting and judging LCA data
Use the data, not opinion. Name the stage or the figure, say which product is better for that measure, and give a number if you can. For example: "the plastic bag uses 0.9 MJ compared with 1.5 MJ for the paper bag, so it uses less energy to make."
Then weigh the evidence. A bag that is better on energy may be worse on litter. A product that is cheaper may use more water. A fair conclusion often says which is better overall and what it depends on, such as how many times the bag is reused.
Be careful with claims in adverts. Ask whether the LCA covers the whole life, whether the figures are measured or estimated, and who paid for it.
New ways to get metals (Higher tier)
Copper ores are running low, so more copper has to come from low-grade ores. Traditional mining would mean digging up, moving and disposing of huge amounts of rock. Two newer methods avoid this: phytomining and bioleaching.
In phytomining, plants are grown on soil that contains copper compounds. The plants absorb the compounds. The plants are harvested and burned, and the ash contains the copper compounds. The metal is then obtained from the ash. In bioleaching, bacteria use the copper compounds in the ore to make a leachate solution that contains copper compounds.
Copper can then be made from the solution by displacement with scrap iron, or by electrolysis. These methods can use low-grade ores and cause less damage than mining, but they are slow, and phytomining needs a lot of land. When you evaluate, give an advantage, a disadvantage and a judgement.
Recap
Reduce, reuse and recycle to save limited resources, energy and landfill. Recycled metals and glass need less energy than new ones.
An LCA looks at raw materials, manufacture and packaging, use, and disposal, with transport at each stage. It is not purely objective, and it can be misused.
To compare products, use the data from each stage, divide by the number of uses where needed, and give a conclusion.
Key points
Reduce, reuse, recycle. Recycling saves ore, energy and landfill space. It still needs collecting and sorting.
LCA stages: extracting and processing raw materials, manufacturing and packaging, use and operation, disposal. Transport at each stage.
Water, energy and waste are easy to measure. Pollutant effects need value judgements, so an LCA is not purely objective.
Higher tier: phytomining uses plants, bioleaching uses bacteria. Copper is made from the solutions by displacement with scrap iron or by electrolysis.
Worked examples
Example 1
Name the four stages assessed in a life cycle assessment.
The life cycle starts with getting the raw materials.
The product is then manufactured and packaged, and then used.
Last it is disposed of at the end of its useful life.
Answer: Extracting and processing raw materials, manufacturing and packaging, use and operation, and disposal
Common slips
Slip: Making, selling, buying, breaking. These are not the standard stages of an LCA.
Slip: Only the use stage. An LCA covers the whole life of a product, not just one stage.
Slip: Disposal comes first. Disposal is the last stage.
Example 2
A plastic bag needs 0.9 MJ of energy to make. A paper bag needs 1.5 MJ. The paper bag is used 3 times and the plastic bag is used once. Calculate the energy per use for each bag and say which is lower.
Plastic bag: 0.9 ÷ 1 = 0.9 MJ per use.
Paper bag: 1.5 ÷ 3 = 0.5 MJ per use.
0.5 is less than 0.9.
The paper bag has the lower energy per use.
Answer: Plastic 0.9 MJ per use, paper 0.5 MJ per use, so the paper bag is lower
Common slips
Slip: Plastic 0.9 MJ and paper 4.5 MJ. You multiplied by the number of uses. Divide to find the energy per use.
Slip: The plastic bag is lower because 0.9 is less than 1.5. Compare the energy per use, not the energy to make each bag.
Slip: Paper 1.5 ÷ 3 = 2 MJ. Check the division. 1.5 ÷ 3 = 0.5.
Slip: They are equal. The two figures are different, 0.9 and 0.5.
Example 3
Aluminium cans can be made from ore or from recycled cans. Making a can from ore uses 8.0 MJ of energy. Making a can from recycled aluminium uses 5% of this. Calculate the energy to make a can from recycled aluminium and give two other advantages of recycling aluminium.
5% of 8.0 = 0.05 × 8.0.
0.05 × 8.0 = 0.40 MJ.
Recycling saves aluminium ore, so the supply lasts longer.
Recycling reduces landfill and the damage caused by mining.
Answer: 0.40 MJ. It saves ore and reduces landfill and mining damage
Common slips
Slip: 8.0 × 5 = 40 MJ Convert 5% to 0.05 before multiplying.
Slip: 8.0 ÷ 5 = 1.6 MJ That is one fifth, not 5%. Use 0.05 × 8.0.
Slip: Recycling makes more waste. Recycling reduces the waste that goes to landfill.
Slip: Recycling uses more energy. In this question recycling uses 0.40 MJ instead of 8.0 MJ, so it uses less energy.
Questions and answers
Life cycle assessments, recycling and getting metals sustainably practice questions for GCSE Combined Science Chemistry. Try each one, then open the answer. Easy questions come first.
Question 1 Easy
What do the letters LCA stand for?
Show answer
Answer: life cycle assessment
LCA compares the environmental impact of products.
It stands for life cycle assessment.
Question 2 Easy
Name the first stage of a life cycle assessment.
Show answer
Answer: extracting and processing raw materials
A product starts with its raw materials.
The first stage is extracting and processing raw materials.
Question 3 Easy
Name the last stage of a life cycle assessment.
Show answer
Answer: disposal
The life cycle ends when the product is no longer useful.
The last stage is disposal.
Question 4 Easy
Does recycling aluminium use more or less energy than extracting it from its ore?
Show answer
Answer: less
Melting scrap aluminium is far cheaper in energy than electrolysis of the ore.
It uses less energy.
Question 5 Easy
Name one material that is recycled by melting and recasting.
Show answer
Answer: metal
Metals and glass can be melted and reformed.
For example a metal.
Question 6 Medium
Which is easier to measure in an LCA: the energy used or the damage done by a pollutant?
Show answer
Answer: the energy used
Energy can be measured.
The harm done by a pollutant needs a value judgement.
Question 7 Medium
Scrap steel is added to iron from a blast furnace. What does this reduce the need to extract?
Show answer
Answer: iron
The scrap steel contains iron already.
So less iron needs to be extracted from iron ore.
Question 8 Medium
A plastic bag needs 0.9 MJ of energy to make and a paper bag needs 1.5 MJ. How many times as much energy does the paper bag need? Give your answer to 2 significant figures.
Show answer
Answer: 1.7
Divide the paper figure by the plastic figure.
1.5 ÷ 0.9 = 1.67, which is 1.7 to 2 significant figures.
Exam-style questions
Longer questions in the style of a written paper, with the marking points. These are Yumio practice questions.
Exam-style question 14 marks
(a) State two stages in the life of a product that are assessed in a life cycle assessment (LCA). [2 marks] (b) Explain why an LCA is not a purely objective process. [2 marks]
Show answer and marking points
Answer: (a) extracting and processing raw materials and disposal at the end of its life (b) some effects, such as pollutants, cannot be easily measured so value judgements are needed, and a selective LCA can be used to support a claim
(a) first stage, for example extracting raw materials, manufacture, use (1)
(a) second stage, for example disposal (1)
(b) pollutant effects are hard to give numbers to or need value judgements (1)
(b) a selective LCA can be misused or biased, for example for advertising (1)
Exam-style question 24 marks
(a) Give two advantages of recycling metals. [2 marks] (b) Give one disadvantage of recycling metals. [1 mark] (c) Give one way a person can reduce the use of limited resources. [1 mark]
Show answer and marking points
Answer: (a) it saves ore and energy (b) the metal has to be collected and sorted which costs money (c) reuse glass bottles
(a) saves ore or resources (1)
(a) saves energy, or reduces landfill, or reduces damage from mining (1)
(b) collecting, sorting or transporting costs money or energy (1)
(c) reduce, reuse or recycle, for example reuse a bag (1)
Common mistakes
Saying an LCA only looks at the use of a product
It covers raw materials, manufacture and packaging, use, and disposal, with transport at each stage.
Saying an LCA is always fair and objective
Putting values on pollution needs judgements, and a selective LCA can be misused for advertising.
Saying recycling uses no energy
Recycling still needs energy for collecting, sorting and melting, but usually much less than making from ore.
Saying glass can only be thrown away
Glass bottles can be reused, or crushed and melted to make new glass products.
Comparing totals without thinking about number of uses
Divide the impact by the number of times the product is used.
Questions students ask
Is Life cycle assessments, recycling and getting metals sustainably on the Foundation or Higher tier?
Life cycle assessments, recycling and getting metals sustainably is on both Foundation and Higher papers for GCSE Combined Science Chemistry, aimed at around grade 5.
What is a common mistake on Life cycle assessments, recycling and getting metals sustainably?
Saying an LCA only looks at the use of a product. It covers raw materials, manufacture and packaging, use, and disposal, with transport at each stage.
Where are the answers to the Life cycle assessments, recycling and getting metals sustainably questions?
Open Show answer under each question on this page. The questions are Yumio practice questions, not past exam questions.